Steering wheel with integrated gas bag

ABSTRACT

A steering wheel has a skeleton with a foamed sheathing, a hub, spokes and a steering wheel rim. A gas bag module is inserted in a central recess of the steering wheel. The gas bag module has a cover cap at the side facing the driver. For actuating a horn switch the module is movable in the direction of the steering wheel axis relative to the steering wheel. A movement gap is formed between the cover cap and the foamed sheathing. Mounting studs on the skeleton extend parallel to the steering wheel axis. The positioning of the mounting studs is defined by the foamed sheathing. The mounting studs have free ends which are slidingly accommodated in guide recesses provided in the cover cap.

RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 09/272,281, filed on Mar. 19, 1999 which claims priority ofGerman Application No. 298 05 207.5, filed Mar. 23, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to a steering wheel having a skeletonprovided with a foamed sheathing, a hub, spokes and a steering wheelrim, and including a gas bag module which is inserted in a centralrecess of the steering wheel, with a cover cap at the side facing thedriver.

Numerous proposals have already been made for securing a gas bag modulein a steering wheel. When steering wheels in the final assembly aresecured by means of a nut screwed to the end of the steering column, thegas bag module cannot be inserted until the steering wheel has beenfitted since the module is located centrally above the steering wheelhub which must remain freely accessible for screwing on the nut.Alternatively, when the steering wheel is furnished with the completelyassembled gas bag and is mounted to the steering column, then some othermeans of securing the steering wheel is needed. For this, proposals havealready been made as well, but all of which are more expensive in designand thus more costly than the usual solution of securing the steeringwheel by a central nut.

If the gas bag cover is to be used for actuating the horn switch, thegas bag module needs to be shiftably arranged in the steering wheel,allowing for a contact stroke parallel to the steering wheel axis.

With many mounting systems for gas bag module in a steering wheel, it isa nuisance that the cover cap on the side facing the driver may bepositioned relative to the surface of the steering wheel only withconsiderable complication such that movement gaps existing between thecover cap and the steering wheel, as needed for actuating the hornswitch, are equally wide, because between any fastening points at whichbolts are inserted and these portions in which movement gaps areprovided, a plurality of components is arranged whose inevitableproduction tolerance in the worst case add up, resulting insignificantly differing wide movement gaps. This is unacceptable interms of a neat appearance.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to provide a steering wheel with afastening means permitting to maintain any movement gaps within closetolerances, using conventional bolt connections to reduce productioncost, and without necessitating additional space.

To achieve this object it is proposed in accordance with the inventionthat mounting studs are provided which extend parallel to the steeringwheel axis. The positioning of these studs is defined and determined bya foamed sheathing which covers the steering wheel rim and at least partof the spokes. The cover cap has recesses wherein free ends of themounting studs are slidingly received.

In this arrangement it is assumed that the constructional alignmentcoordinates, for correctly positioning the cover cap relative to thesteering wheel surface, need to be provided as near as possible to themovement gaps and where possible in the same component which inconjunction with the cover cap itself is responsible for the width ofthe movement gap to be judged by appearance only. This is the foamedsheathing applied to the steering wheel. When in accordance with theinvention the portions juxtaposing the cover cap are produced in thesame mold and in the same step of production as the coordinatesdetermining the positioning, then the production tolerances may bereduced to such an extent that they are no longer able to influence themovement gaps.

The mounting studs to be used in accordance with the invention areaccordingly positioned in the foamed sheathing and so preciselydetermine the positioning of the cover cap which in turn is attachableto the mounting studs by the guide recesses in the cover cap. It willreadily be appreciated that the movement gaps may be very closelytoleranced in this way, particularly when the mounting studs arearranged directly juxtaposing the movement gaps where possible.

The gas bag module may be preassembled with the cover cap via themounting studs and then inserted together with the cover cap in thesteering wheel already arranged in the vehicle. Subsequently, all thatis needed is to tighten the studs on the rear side of the steeringwheel, this corresponding to the present scope of work in fitting boltconnections.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will now be discussed by way ofembodiments illustrated in the drawings, wherein

FIG. 1 is a partial section through a steering wheel incorporating afirst embodiment of the gas bag module mounting.

FIG. 2 is a section through a steering wheel incorporating a secondembodiment of the gas bag module mounting.

FIG. 3 illustrates a variant of the embodiments as shown in FIGS. 1 and2 as regards the attachment region of the cover cap.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 there is illustrated a partial section of asteering wheel in which a skeleton consisting of a hub 1, spokes 2 and asteering wheel rim 3 is provided with a foamed sheathing 4. The gas bagmodule 5 comprising a cover cap 6 at the side facing the driver isinserted in a pot-shaped cavity in the steering wheel, a movement gap 7being provided between the foamed sheathing 4 and the cover cap 6. Formovingly securing the gas bag module 5, mounting studs 10 are providedwhich extend parallel to the steering wheel axis. The positioning of themounting studs 10 is defined by the foamed sheathing 4, largishfoam-coated through-holes 9 being provided for this purpose in thespokes 2. Provided concentrically to the foam-coated through-holes 9 andon the upper and lower sides of the foamed sheathing 4 are supportingportions 8 and 8′ extending in a plane perpendicular to the steeringwheel axis. These supporting portions 8, 8′ serve as a buttress for thebolt connection, a flange 11 of the mounting stud 10, on the one hand,and the head of a bolt 12, on the other, resting on the supportingportions 8, 8′ in the fitted condition. Arranged above the flange 11 isa washer 13 of an insulating material in which a support for the hotelectrical contacts 14 is embedded. At the end of the mounting stud 10,at the side facing the driver, a nut 21 is screwed in place, the finalfitted positioning of which is defined by a stop on the mounting stud10. The cover cap is attached to the nut 21 by means of a guide recess25.

Clamped in place between the nut 21 and the washer 13 of insulatingmaterial is a helical spring 15 and the dished recess 19 of a mountingtab 17 of the gas bag module 5. Secured to the mounting tab 17 is anelectrical mass contact 18. Additionally arranged between the nut 21 andthe dished recess 19 of the mounting tab 17 is a washer 35 ofnoise-dampening material.

In the embodiment shown the gas bag module 5 comprises an inflator 16with a mounting flange 16′ to which the gas bag 36 is secured via amounting ring (not shown). By means of the same fasteners an inwardlyangled tab 23′ of a surrounding web 23 of the cover cap 6 and themounting tab 17 are secured. Gas bag module 5 and cover cap 6 thus forman assembly unit which is positioned relative to the foamed sheathing 4via the guide recess configured in the cover cap 6. The dished recess 19of the mounting tab 17 comprises for this purpose a through-hole 20, thediameter of which is larger by the required clearance than the outerdiameter of the mounting stud 10. Reference numeral 24 identifies theouter portion of the cover cap 6, i.e. the portion forming together withthe foamed sheathing 4 the movement gap 7 in the fitted condition.

The assembly consisting of gas bag module 5 and cover cap 6 ispositioned in a plane perpendicular to the steering wheel axis by themounting stud 10 relative to the steering wheel whilst being arrangedsuch that for actuating the horn switch contacts 14 and 18, it may bedepressed parallel to the steering wheel axis and against the resistanceof the return spring 15. For fitting the assembly unit consisitng of gasbag module 5 and cover cap 6, the mounting studs 10 are inserted intothe foam-coated through-holes and secured to the steering wheel via thebolts 12, the foamed sheathing 4 being configured such that the boltsare unable to drop out downwards even when totally screwed out of thethreaded bore of the mounting stud.

Referring now to FIG. 2 there is illustrated an embodiment employingsimilar mounting studs 10 including a thickened portion 26 at one endwhich in the fitted condition engages blind holes 9′ in the foamedsheathing 4. In this arrangement two mounting studs 10 each areconnected to a plate 28 through washers 13 of an insulating materialsuch that any clearance needed for positioning the mounting studs 10 inthe foamed sheathing 4 is maintained.

The plate 28 carries the hot electrical contacts 33 whilst the masscontacts are carried by a mounting plate 30 secured to the gas bagmodule. The mounting plate 30 is, the same as in the embodiment as shownin FIG. 1, provided with mounting tabs 17 which for actuating the hornswitch contacts may be depressed parallel to the steering wheel axis ormay be tilted. The cover cap 6 is, here again, attached by means ofguide recesses 25 to the nuts 21 screwed onto the mounting studs 10, atthe side facing the driver.

Unlike the embodiment as shown in FIG. 1, however, here in FIG. 2 asnap-in or latch-type connection is provided, comprising for twofastening points each a snap-action stud 29 extending in the directionof the steering wheel axis and a latching pawl secured to the mountingplate 30. The snap-action stud 29 is secured by its rear end in askeleton part 1 of the steering wheel and provided by known ways andmeans with a conical front end, it being by this end that thesnap-action stud 29 is able to pass through a through-opening 31 in themounting plate 30 to engage behind a latching pawl 32 in the finishedfitted condition. By means of such a snap-in or latch-type connectionthe time needed for final assembly of the gas bag module may, of course,be further reduced as compared to a bolt connection.

It is understood that components in the scope of the descriptionrelating to FIG. 2 and not identified by reference numerals are the samein configuration and function as those already described regarding theembodiment as shown in FIG. 1.

Referring now to FIG. 3 there is illustrated a variant which differsfrom the embodiments as shown in FIGS. 1 and 2 merely by the cover cap 6with a guide recess 25′ being directly attached to the end, at the sidefacing the driver, of the mounting stud 10, 26 and not to the nut 21′.In this way it is prevented that the unavoidable thread clearancebetween the nut 21′ and the mounting stud 10, 26 influences the movementgap 7 between cover cap 6 and foamed sheathing 4.

It is evident from the magnified illustration as shown in FIG. 3 thatbetween the outer limitation of the mounting stud 10, 26 and thesurrouding component a radial clearance is provided so that thiscomponent cannot obstruct orienting the cover cap 6 relative to thefoamed sheathing 4 in a plane perpendicular to the steering wheel axis.Thus, there is provided a way of securing a gas bag module in a steeringwheel, in which the cover cap may be precisely oriented in a planeperpendicular to the steering wheel axis, the cover cap, however, beingarranged movable and parallel to the axis for actuating the horncontacts.

In the embodiment as shown in FIG. 1 the mounting studs are designedsuch that they are able to take up the reaction forces occurring onactuation of the gas bag, they being made of steel or some otherhigh-tensile material. In the embodiment as shown in FIG. 2 the reactionforces are taken up by the snap-in or latch-type connections, so thatthe mounting studs as regards their strength need to be designed merelyfor positioning the cover cap relative to the steering wheel. For thesepurposes they may be made of suitable synthetic materials, thus makingfor an additional weight-saving as compared to the embodiment as shownin FIG. 1.

What is claimed is:
 1. A steering wheel having a skeleton, said steeringwheel comprising: a hub, a plurality of spokes, a steering wheel rim,and a foamed sheathing surrounding at least said steering wheel rim andpart of said spokes, and a gas bag module having a cover cap beingprovided in said steering wheel, said gas bag module being movablerelative to said skeleton for actuation of a horn switch, an apparentgap being formed between said cover cap and said foamed sheathing, saidgas bag module being movably secured in said steering wheel by aplurality of mounting studs having free threaded ends projecting towardsaid cover cap, said cover cap having recesses aligned with saidmounting studs for accommodation of said free ends of said mountingstuds, and said sheathing providing positional relationship between saidskeleton, said mounting studs and said cover cap recesses, and saidsteering wheel further comprising blind holes being provided in saidfoamed sheathing, said foamed sheathing providing supporting areasaround said blind holes, and each of said mounting studs having aflange, said flanges of said mounting studs bearing on said supportingareas of said foamed sheathing, said supporting areas thus formingbuttresses for said mounting studs.
 2. A steering wheel according toclaim 1, wherein each of said mounting studs has a rear end accommodatedin one of said blind holes, said rear ends of said mounting studs eachengaging a widened portion of said blind holes by means of a thickenedportion.
 3. A steering wheel having a skeleton, said steering wheelcomprising: a hub, a plurality of spokes, a steering wheel rim, and afoamed sheathing surrounding at least said steering wheel rim and partof said spokes, and a gas bag module having a cover cap being providedin said steering wheel, said gas bag module being movable relative tosaid skeleton for actuation of a horn switch, an apparent gap beingformed between said cover cap and said foamed sheathing, said gas bagmodule being movably secured in said steering wheel by a plurality ofmounting studs having free threaded ends projecting toward said covercap, said free threaded ends being provided with nuts screwed on saidthreaded ends of said mounting studs, said cover cap having recessesaligned with said mounting studs, said nuts are configured forattachment of said recesses of said cover cap, and said sheathingproviding positional relationship between said skeleton, said mountingstuds, and said cover cap recesses.
 4. A steering wheel according toclaim 3, wherein each of said mounting studs has a flange, and saidsteering wheel comprises washers of an insulating material beingarranged above said flanges and return springs being arranged betweensaid nuts screwed on said threaded ends of said mounting studs and saidwashers of insulating material, and said return springs being preloadedby means of said nuts screwed on said threaded ends of said mountingstuds.
 5. A steering wheel according to claim 4, wherein said mountingstuds are carried by a plate mounted between said washers of insulatingmaterial, said plate being provided with electrical contacts, and saidmounting studs being connected to said plate in a manner to permitalignment of said mounting studs in said foamed sheathing.
 6. A steeringwheel having a skeleton, said steering wheel comprising: a hub, aplurality of spokes, a steering wheel rim, and a foamed sheathingsurrounding at least said steering wheel rim and part of said spokes,and a gas bag module having a cover cap being provided in said steeringwheel, said gas bag module being movable relative to said skeleton foractuation of a horn switch, an apparent gap being formed between saidcover cap and said foamed sheathing, said gas bag module being movablysecured in said steering wheel by a plurality of mounting studs havingfree threaded ends projecting toward said cover cap, said cover caphaving recesses aligned with said mounting studs for accommodation ofsaid free ends of said mounting studs, and said sheathing providingpositional relationship between said skeleton, said mounting studs andsaid cover cap recesses, and said steering wheel further comprising amounting plate having a central through-hole, a snap-action stud havingan end attached to said skeleton and a latching pawl provided on saidmounting-plate, said snap-action stud being adapted to pass through saidthrough-hole of said mounting plate and to engage behind said latchingpawl.